Field of the Invention
The present invention relates in general to cranes and has specific reference to a hoisting device capable of positioning in the space a load by means of a high-power crane, for example a crane having a load capacity of over 300 tons.
It is known that positioning a heavy load suspended by means of several ropes from the jib of a crane constitutes a difficult problem, since the length of each rope is invariable and the load, when hoisted, has not compulsorily the desired orientation.
To avoid this difficulty, cranes comprising two or more suspension hooks have been proposed in the past, but they require for their operation ropes having an abnormally great diameter which cannot be handled manually and therefore make it necessary to use auxiliary cranes. Moreover, these huge cranes are equipped with extremely heavy tackles, which is also a serious inconvenience.